Method and system for hollow cathode plume photochromic inversion of electron temperature

Abstract

The invention provides a method and a system for hollow cathode plume light color inversion of electron temperature, which are suitable for inversion diagnosis of hollow cathode electron temperature distribution in on-orbit or other vacuum environments. The method is based on hollow cathode plume light color data extraction, two-dimensional processing of plume light color data, establishment of a correlation database of grid light color with respect to electronic temperature, and inversion of electronic temperature distribution by using the grid light color. According to the method, electron temperature inversion data and Langmuir probe measurement data are consistent in trend, the diagnosis deviation is within 30%, and based on the method, researchers can directly use hollow cathode plume pictures to quickly diagnose electron temperature distribution characteristics in a non-contact mode.

Description

Technical Field

[0001] The present invention relates to the field of computing, and in particular to a method and system for inverting electron temperature from hollow cathode plume light color. Background Art

[0002] In the field of electric propulsion, hollow cathode plays a critical role. It uses the thermal electron emission mechanism to greatly reduce the vacuum barrier of solid electron emission, not only providing ignition electrons and neutralization electrons for thrusters, but also one of the decisive factors for the performance of electric thrusters.

[0003] The electron temperature characteristics inside the hollow cathode are of great significance. They are directly related to the electron emission capability and the working mode of the cathode, and are an indispensable key physical indicator for researchers when designing and optimizing the cathode structure. However, the current technical situation has brought great challenges to the study of the electron temperature inside the hollow cathode. Due to the small internal space of the hollow cathode, it is difficult to accurately measure the internal electron temperature distribution using experimental methods. This undoubtedly sets up many obstacles for the in-depth exploration of the internal mechanism of the hollow cathode and the optimization and upgrading of its performance, making non-contact diagnosis of the electron temperature inside the hollow cathode the focus of current scientific research.

[0004] Up to now, among the relevant studies, only the literature "Dan G, Kristina J, Ron W, et al. Hollow Cathode Theory and Experiment. I. Plasma Characterization Using Fast Miniature Scanning Probes. Journal of Applied Physics. 2005, 98: 1-9" has attempted to diagnose the inside of the hollow cathode using a single Langmuir probe. This is a single fine needle with a diameter of only 0.5 mm. The electron temperature inside the cathode can be obtained by quickly entering and exiting the cathode top hole area (wall probe erosion) combined with voltage rapid scanning technology. However, the literature also mentioned that this method has a certain degree of damage to the electron movement inside the cathode, causing deviations in the measurement results, making it difficult to accurately reflect the actual electron temperature inside the hollow cathode.

[0005] Through searching patent documents, it was found that the invention patent with publication number CN118067401A discloses an on-orbit imaging monitoring device and method for the coupling state of Hall thrusters and cathodes. The method first conducts an imaging monitoring experiment of the coupling state of Hall thrusters and cathodes in a ground experiment to obtain the electron temperature of the electron bridge in the coupling area of ​​the Hall thrusters under various working conditions; then the electron temperature of the electron bridge in the coupling area is measured on the satellite, and the electron temperature measured at this time is compared with the electron temperature of the same working condition in the ground experiment. If the two are consistent, it indicates that the coupling state of the Hall thrusters and cathodes is good at this time. If the two are inconsistent, adjust the voltage, current of the Hall thrusters and the current of the hollow cathode until the two are consistent. This patent mainly focuses on the monitoring of the coupling state of the Hall thrusters and cathodes and the adjustment method of the coupling state. There are deficiencies in the precise correlation database of plume light color-electron temperature and the capture of the precise position of the electron temperature.

[0006] In summary, in response to the above-mentioned problems of the prior art, studying a method and system for inverting electron temperature from the light color of a hollow cathode plume has become a key task that needs to be solved urgently. Summary of the invention

[0007] In view of the defects in the prior art, the object of the present invention is to provide a method and system for inverting electron temperature from hollow cathode plume light color.

[0008] According to the present invention, a method for inverting electron temperature from hollow cathode plume light color is provided, comprising the following steps:

[0009] Step S1, extracting RGB data from the hollow cathode photo, and performing grid differential fitting on the extracted RGB data to obtain fitted RGB data;

[0010] Step S2, performing two-dimensional profile separation on the fitted RGB data to obtain profile RGB data;

[0011] Step S3, based on the cross-section RGB data and in accordance with the atomic energy level transition rules, a correlation database of grid radiation light colors with respect to different electron temperatures is established;

[0012] Step S4, inverting the electron temperature distribution based on the profile RGB data and the associated database.

[0013] Preferably, step S1 includes the following sub-steps:

[0014] Step S1.1, based on the characteristics of the electric propulsion hollow cathode plume, the brightest point of the plume, the cathode-plume boundary, the anode-plume boundary and the cathode central axis are captured to obtain the cathode plume area envelope, and the RGB data within the plume area envelope is extracted;

[0015] Step S1.2, differential fitting is performed on the RGB data (based on the photo pixel grid) to the computational domain grid points to obtain the fitted RGB data, presenting a three-dimensional rotating body shape.

[0016] Preferably, in step S1.2, the difference method is area-weighted difference, that is, the greater the difference weight, the greater the influence of the difference point on the computational domain grid node.

[0017] Preferably, step S2 includes the following sub-steps:

[0018] Step S2.1, first layer peeling: based on the fitted RGB data, select the single-color point at the top of the three-dimensional plume that has not been color-superimposed, and use the single-color point to eliminate the color superposition brought by the first layer of the circumference where the single-color point is located;

[0019] Step S2.2, second layer peeling: when the second monochrome point appears at the top of the second layer of the plume, the second monochrome point is also used to eliminate the color superposition brought by the second layer of the plume;

[0020] Step S2.3, and so on, after n times of peeling, the light color of the entire photo is processed into monochrome points to obtain the profile RGB data required for calculation.

[0021] Preferably, the shelling process includes: if a visual line is formed by superimposing m single-color points, the superimposed color is (r 1 , g 1 , b 1 ), the color of a single monochrome point is (r p , g p , b p ), according to the rotational symmetry, among the m monochromatic points, the colors of two points (the front end and the rear end of the visual field) are the same as the color of a single monochromatic point, which is the actual color data of the shelling circle. After shelling, the visual line is left with the color superposition of (m-2) points. At this time, the color is recorded as (r 2 , g 2 , b 2 ), the calculation formula is as follows:

[0022]

[0023] Preferably, in step S3, the atomic energy level transition rule considers eight transition lines from the high energy level to the low energy level of the Xe atom, specifically 8p→7p, 8p→6s 1 '、8p→6s 1 、6p'→6s 1 '、6p'→6s 1 、7p→6s 1 、6s 1 '→1S 0 and 6s1 →1S 0 The corresponding transition probabilities are 1 / 2500, 1 / 333, 1 / 333, 1 / 1690, 1 / 1450, 1 / 658, 1 / 3.79 and 1 / 3.17 respectively.

[0024] Preferably, in step S3, based on the electron scattering cross sections of the eight transition lines, the corresponding electron temperatures, and assuming that the background atomic number density in the grid is uniformly distributed, the radiation light colors of the eight transition lines of gas discharge corresponding to the Xe central gas at different electron temperatures are obtained, and the radiated light colors are superimposed so that any electron temperature in the grid corresponds to a unique grid background gas light color, that is, "light color" and "temperature" are one-to-one corresponding, and then an associated database is established.

[0025] Preferably, step S4 includes the following sub-steps:

[0026] Step S4.1, based on the cross-sectional RGB data, using the associated database to determine the specific temperature value that triggers the photochromic electrons;

[0027] Step S4.2, the difference between the position where the atom undergoes an excitation collision and the position where the atom radiates a photon is the atomic distance corresponding to the lifetime of the atom's excited state. If the background atomic number density distribution and velocity distribution are given, the atomic distance corresponding to the lifetime of the atom's excited state is reversely subtracted from the position where the atom radiates a photon to obtain the position where the atom undergoes an excitation collision, that is, the position corresponding to the electron temperature;

[0028] Step S4.3, obtaining electron temperature distribution data by combining the specific temperature value and the position corresponding to the electron temperature.

[0029] Preferably, in step S4.2, the value of the atomic excited state lifetime is the inverse of the transition probability.

[0030] The present invention also provides a system for inverting electron temperature from hollow cathode plume light color, comprising:

[0031] Module M1, extracts RGB data from the hollow cathode photo, and performs grid differential fitting on the extracted RGB data to obtain fitted RGB data;

[0032] Module M2, performs two-dimensional profile separation on the fitted RGB data to obtain profile RGB data;

[0033] Module M3, based on the profile RGB data and according to the atomic energy level transition rules, establishes a correlation database of grid radiation light colors with different electron temperatures;

[0034] Module M4 inverts the electron temperature distribution based on the profile RGB data and the associated database.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The present invention performs inversion diagnosis on the electron temperature distribution of the hollow cathode in orbit or other vacuum environments. The electron temperature diagnosis data is consistent with the trend of the Langmuir probe diagnosis data, and the diagnosis deviation is within 30%.

[0037] 2. The present invention performs non-contact diagnosis of the electron temperature inside the hollow cathode, which is beneficial for researchers to carry out optimization design work on cathode performance.

[0038] 3. The present invention only requires hollow cathode plume photos as input data, and can quickly analyze cathode performance data in photos in literature, in-orbit or ground test photos, laying the foundation for related image recognition technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0040] Figure 1 It is a schematic diagram of the two-dimensional cross-section separation process in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0042] The present invention innovatively proposes a non-contact plume light color inversion electron temperature diagnostic method specifically for hollow cathodes. Focusing on the cathode plume photo, it first performs accurate color data capture and meticulous data processing, and then cleverly calculates the atomic de-excitation energy level corresponding to the light color based on the principle of radiation energy level spectrum and light color superposition, and finally successfully infers the corresponding electron temperature data. This unique method combines experimental photos and numerical algorithms, and is a semi-theoretical and semi-experimental diagnostic mode. It opens up a new and effective technical path for hollow cathode electron temperature distribution diagnosis, fills the gap in the existing technology, and greatly promotes the development and progress of hollow cathode related research.

[0043] The present invention is only applicable to the commonly used hollow cathodes in electric propulsion, that is, the cathode has the characteristics of hollow ventilation, beam effect-enhanced ionization rate, and emitter with thermal electron emission mechanism. If it exceeds this applicable scope, uncertain diagnostic errors may occur.

[0044] Embodiment 1:

[0045] This embodiment provides a method for inverting electron temperature from hollow cathode plume light color, comprising the following steps:

[0046] Step S1, extracting RGB data from the hollow cathode photo, and performing grid differential fitting on the extracted RGB data to obtain fitted RGB data.

[0047] Specifically, step S1 includes the following sub-steps:

[0048] Step S1.1, based on the characteristics of the electric propulsion hollow cathode plume, capture the brightest point of the plume, the cathode-plume boundary, the anode-plume boundary and the cathode center axis, obtain the cathode plume area envelope, and extract the RGB data within the plume area envelope.

[0049] Step S1.2, differential fitting is performed on the RGB data (based on the photo pixel grid) to the computational domain grid points to obtain the fitted RGB data, presenting a three-dimensional rotating body shape.

[0050] In this embodiment, the difference method is area weighted difference, that is, the greater the difference ratio, the greater the influence of the difference point on the computational domain grid node.

[0051] Step S2, performing two-dimensional profile separation on the fitted RGB data to obtain profile RGB data.

[0052] Figure 1 It is a schematic diagram of the two-dimensional cross-section separation process in an embodiment of the present invention.

[0053] like Figure 1 As shown, step S2 includes the following sub-steps:

[0054] Step S2.1, first layer peeling: Based on the fitted RGB data, select the single-color point at the top of the three-dimensional plume that has not been color superimposed, and use the single-color point to eliminate the color superposition brought by the first layer of the circumference where the single-color point is located.

[0055] Step S2.2, second layer peeling: when the second monochrome point appears at the top of the second layer circumference of the plume, the second monochrome point is also used to eliminate the color superposition brought by the second layer circumference.

[0056] Step S2.3, and so on, after n times of peeling, the light color of the entire photo is processed into monochrome points to obtain the profile RGB data required for calculation.

[0057] Specifically, the shelling process includes: if a visual line is formed by superimposing m single-color points, the superimposed color is (r 1 , g 1 , b 1 ), the color of a single monochrome point is (r p , gp , b p ), according to the rotational symmetry, among the m monochromatic points, the colors of two points (the front end and the rear end of the visual field) are the same as the color of a single monochromatic point, which is the actual color data of the shelling circle. After shelling, the visual line is left with the color superposition of (m-2) points. At this time, the color is recorded as (r 2 , g 2 , b 2 ), the calculation formula is as follows:

[0058]

[0059] Step S3, based on the profile RGB data and in accordance with the atomic energy level transition rules, a correlation database of grid radiation light colors with respect to different electron temperatures is established.

[0060] This embodiment takes Xe as an example and considers the eight transition lines from the high energy level to the low energy level of the Xe atom, specifically 8p→7p, 8p→6s 1 '、8p→6s 1 、6p'→6s 1 '、6p'→6s 1 、7p→6s 1 、6s 1 '→1S 0 and 6s 1 →1S 0 The corresponding transition probabilities are 1 / 2500, 1 / 333, 1 / 333, 1 / 1690, 1 / 1450, 1 / 658, 1 / 3.79 and 1 / 3.17 respectively.

[0061] Specifically, based on the electron scattering cross-sections of the eight transition lines, the corresponding electron temperatures, and assuming that the background atomic number density in the grid is uniformly distributed, the radiation colors of the eight transition lines of gas discharge corresponding to the Xe central gas at different electron temperatures are obtained, and the radiated light colors are superimposed so that any electron temperature in the grid corresponds to a unique grid background gas color, that is, "light color" and "temperature" are one-to-one corresponding, and then an associated database is established.

[0062] Step S4, inverting the electron temperature distribution based on the profile RGB data and the associated database.

[0063] Step S4 includes the following sub-steps:

[0064] Step S4.1, based on the profile RGB data, use the associated database to determine the specific temperature value that triggers the photochromic electrons.

[0065] Step S4.2, the difference between the position where the atom undergoes an excitation collision and the position where the atom radiates photons is the atomic distance corresponding to the atomic excited state lifetime. If the background atomic number density distribution and velocity distribution are given, the atomic distance corresponding to the atomic excited state lifetime is reversely subtracted from the position where the atom radiates photons to obtain the position where the atom undergoes an excitation collision, that is, the position corresponding to the electron temperature.

[0066] The numerical value of the atomic excited state lifetime is the inverse of the transition probability.

[0067] Step S4.3, obtaining electron temperature distribution data by combining the specific temperature value and the position corresponding to the electron temperature.

[0068] Embodiment 2:

[0069] The present invention also provides a system for inverting the electron temperature of a hollow cathode plume by light color. The system for inverting the electron temperature of a hollow cathode plume by light color can be realized by executing the process steps of the method for inverting the electron temperature of a hollow cathode plume by light color. That is, those skilled in the art can understand the method for inverting the electron temperature of a hollow cathode plume by light color as a preferred embodiment of the system for inverting the electron temperature of a hollow cathode plume by light color.

[0070] System, including:

[0071] Module M1, extracts RGB data from the hollow cathode photo, and performs grid differential fitting on the extracted RGB data to obtain fitted RGB data;

[0072] Module M2, performs two-dimensional profile separation on the fitted RGB data to obtain profile RGB data;

[0073] Module M3, based on the profile RGB data and according to the atomic energy level transition rules, establishes a correlation database of grid radiation light colors with different electron temperatures;

[0074] Module M4 inverts the electron temperature distribution based on the profile RGB data and the associated database.

[0075] The spirit and principle of the present invention include: extracting RGB color data and performing data differential fitting operations on cathode plume photos, and then using the shelling method to separate the RGB data of the plume in the form of a three-dimensional rotating body into two-dimensional profile data, and then establishing a database of grid radiation light colors related to different electron temperatures, and inverting the electron temperature distribution data based on the database and the atomic path corresponding to the atomic excited state lifetime. All empirical coefficient corrections, cathode material replacements, gas type replacements, and formula equivalent transformations performed within this spirit and principle should be included in the protection scope of the present invention.

[0076] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for inverting electron temperature from hollow cathode plume light color, characterized in that: The steps include: Step S1, extracting RGB data from the hollow cathode photo, and performing grid differential fitting on the extracted RGB data to obtain fitted RGB data; Step S2, performing two-dimensional profile separation on the fitted RGB data to obtain profile RGB data; Step S3, based on the cross-section RGB data, establishing a correlation database of grid radiation light colors with respect to different electron temperatures according to atomic energy level transition rules; Step S4, inverting the electron temperature distribution based on the profile RGB data and the associated database.

2. The method for inverting electron temperature from hollow cathode plume light color according to claim 1, characterized in that: The step S1 includes the following sub-steps: Step S1.1, based on the electric propulsion hollow cathode plume characteristics, capture the brightest point of the plume, the cathode-plume boundary, the anode-plume boundary and the cathode central axis, obtain the cathode plume area envelope, and extract the RGB data within the plume area envelope; Step S1.2, performing differential fitting on the RGB data to the computational domain grid points to obtain fitted RGB data, presenting a three-dimensional rotational body shape.

3. The method for inverting electron temperature from hollow cathode plume light color according to claim 2, characterized in that: In the step S1.2, the difference method is area weighted difference, that is, the greater the difference weight, the greater the influence of the difference point on the computational domain grid node.

4. The method for inverting electron temperature from hollow cathode plume light color according to claim 1, characterized in that: The step S2 includes the following sub-steps: Step S2.1, first layer peeling: based on the fitted RGB data, select the single-color point at the top of the three-dimensional plume that has not been color-superimposed, and use the single-color point to eliminate the color superposition brought by the first layer of the circumference where the single-color point is located; Step S2.2, second layer peeling: when a second monochrome point appears at the top of the second layer circumference of the plume, the second monochrome point is also used to eliminate the color superposition brought by the second layer circumference; Step S2.3, and so on, after n times of peeling, the light color of the entire photo is processed into a monochrome point to obtain the profile RGB data required for calculation.

5. The method for inverting electron temperature from hollow cathode plume light color according to claim 4, characterized in that: The shelling process includes: if a visual line is formed by superimposing m single-color dots, the superimposed color is (r1, g1, b1), and the color of a single single-color dot is (r p , g p , b p ), according to the rotational symmetry, among the m monochromatic points, the colors of two points are the same as the color of a single monochromatic point, which is the actual color data of the shelling circle. After shelling, the visual line is left with the color superposition of (m-2) points. At this time, the color is recorded as (r2, g2, b2). The calculation formula is as follows:

6. The method for inverting electron temperature from hollow cathode plume light color according to claim 1, characterized in that: In step S3, the atomic energy level transition rule considers 8 transition lines from the high energy level to the low energy level of the Xe atom, specifically 8p→7p, 8p→6s1', 8p→6s1, 6p'→6s1', 6p'→6s1, 7p→6s1, 6s1'→1S0 and 6s1→1S0, and the corresponding transition probabilities are 1 / 2500, 1 / 333, 1 / 333, 1 / 1690, 1 / 1450, 1 / 658, 1 / 3.79 and 1 / 3.17 respectively.

7. The method for inverting electron temperature from hollow cathode plume light color according to claim 6, characterized in that: In step S3, based on the electron scattering cross sections and corresponding electron temperatures of the eight transition lines, and assuming that the background atomic number density in the grid is uniformly distributed, the radiation light colors of the eight transition lines of gas discharge corresponding to the Xe central gas at different electron temperatures are obtained, and the radiated light colors are superimposed so that any electron temperature in the grid corresponds to a unique grid background gas light color, that is, the light color and the temperature are one-to-one corresponding, and then an associated database is established.

8. The method for inverting electron temperature from hollow cathode plume light color according to claim 1, characterized in that: The step S4 includes the following sub-steps: Step S4.1, based on the cross-sectional RGB data, using the associated database to determine a specific temperature value that triggers the photochromic electrons; Step S4.2, the difference between the position where the atom undergoes an excitation collision and the position where the atom radiates a photon is the atomic distance corresponding to the lifetime of the atom's excited state. If the background atomic number density distribution and velocity distribution are given, the atomic distance corresponding to the lifetime of the atom's excited state is reversely subtracted from the position where the atom radiates a photon to obtain the position where the atom undergoes an excitation collision, that is, the position corresponding to the electron temperature; Step S4.3, combining the specific temperature value and the position corresponding to the electron temperature to obtain electron temperature distribution data.

9. The method for inverting electron temperature from hollow cathode plume light color according to claim 8, characterized in that: In the step S4.2, the value of the atomic excited state lifetime is the inverse of the transition probability.

10. A system for inverting electron temperature from hollow cathode plume light color, characterized in that: include: Module M1, extracts RGB data from the hollow cathode photo, and performs grid differential fitting on the extracted RGB data to obtain fitted RGB data; Module M2, performing two-dimensional profile separation on the fitted RGB data to obtain profile RGB data; Module M3, based on the cross-sectional RGB data, establishes a correlation database of grid radiation light colors with respect to different electron temperatures according to atomic energy level transition rules; Module M4 inverts the electron temperature distribution based on the profile RGB data and the associated database.

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